There have heretofore been developed in the art a great many devices designed to increase the mobility of those persons having one or more of a variety of physical handicaps. In that this area of endeavor is highly populated with invention attests both to the great demand for such devices and to the fact that the known art has been unable to satisfy in all respects this demand.
Known motorized wheelchairs may be generally divided into two categories. One includes those devices which are motorized versions of conventional, collapsible wheel chairs and which have a battery powered motor driving each of the two large rear wheels. The steering, and forward and reverse directions are controlled by a single joy stick which electronically governs the speed of each motor driven wheel and thereby allows directional change by varying the relative speed of each wheel. This wheelchair type is generally restricted to indoor use.
Two problems are associated with this design. First, because of the sophisticated electronics involved, the electric motors and control mechanism are subject to frequent breakdown and subsequent costly repair. Indeed, maintenance of these parts constitutes the overwhelming percentage of the costs associated with their use, not to mention the high initial cost of such a wheelchair.
In addition to the above, there is also the problem of wear and tear on domestic carpeting and other floor coverings. Because movement in the home often requires tight maneuvering, the wheelchair must be able to pivot on one wheel, that is, one wheel is held stationary, while the other is rotated. Many wheelchairs rely solely on this method for directional control. This steering means however, causes severe wearing of the floor covering at the point of pivot which is aggravated by the fact that very narrow diameter tires are required to facilitate the pivot action. A great deal of pressure is thereby centered at the pivot point which can fray carpeting and remove finishes on wood or vinyl flooring.
A second category of motorized wheelchairs comprises the devices generally used out-of-doors. These wheelchairs are somewhat akin to golf carts or go-carts in their manner of operation in that they generally possess a conventional front wheel steering mechanism and rear drive. This layout, although much less maneuverable than the first said design, is much simpler and more rugged and thus better adapted to the more demanding environment out-of-doors. Of course the lack of high maneuverability precludes use indoors except in large open spaces such as a factory or office. Included also in this category are those devices which can accept a conventional, unmotorized wheelchair much like an overland ferry boat. That is, the wheelchair is loaded onto a platform and the occupant drives the device using the wheelchair as a driver's seat. Both of these types of outdoor wheelchairs have the disadvantage that their steering and/or forward and reverse controls require a higher degree of effort to use than the electric means generally used in the indoor type wheelchair.
Heretofore, no one has devised a control mechanism which is both very simple and very rugged in design and yet can be operated by low effort joy stick control. Thus, outdoor wheelchairs of the known art are inappropriate for those really handicapped persons who are unable to exert effort to use the controls.
The prior art includes the following references: U.S. Pat. No. 3,921,740 teaches use of a loading ramp to facilitate movement of a wheelchair onto the floor at the rear of the device; U.S. Pat. No. 3,912,032 concerns use of a tractor assembly to interconnect with a wheelchair providing power therefore; U.S. Pat. No. 2,710,659 teaches use of a tractor unit to be attached to a wheelchair to produce a cart; U.S. Pat. No. 806,295 teaches the use of an electric motor to drive a tractor adapted for receiving a wheelchair.
U.S. Pat. Nos. 3,964,768; 3,955,639; and 1,164,863 present the general concept of motorized wheelchairs. U.S. Pat. Nos. 3,888,324 and 3,671,071 refer to electric vehicles such as are commonly used as golf carts.
In addition, there are currently various motorized wheelchairs on the market such as the Voyager series made by Voyager, Inc. of South Bend, Indiana; the Elektra series made by Sherry Products of Hermosa Beach, California and the Stephen Motorchair made by Stephen Motorchair Company of Siloam Springs, Arizona. These devices possess one or more of the disadvantages discussed above.